1. Field of the Invention
This invention relates to the field of protective enclosures for laboratory and clinical medicine use, and in particular to a mobile enclosure which produces a vertical laminar flow of micro filtered air in an enclosure that permits two-sided manual access under a transparent sidewall to an operating field, and facilitates surgical procedures on laboratory animals as well as on humans.
2. Prior Art
Laboratory work chambers or hoods are well known. In a typical hood the object is to confine fumes produced in chemical reactions to the enclosure defined by the hood, possibly exhausting the fumes by a powered ventilator. The hood typically is operated at a negative pressure differential relative to the outside such that none of the fumes escape. In certain applications the object is to keep particulate matter out of the work area, in which case the work chamber can be operated at positive pressure and provided with a filter for removing particles from air pumped into the enclosure. The outlet of filtered air into the enclosure is disposed in the rear of the work chamber or in the top.
U.S. Pat. No. 4,016,809--Austin discloses a clean air workbench including a HEPA filter for removing particles from air pumped through the rear wall of a work chamber using a fan. The air passes horizontally from the rear wall through an open front of the chamber. U.S. Pat. No. 3,301,167--Howard et al and U.S. Pat. No. 3,363,539--Taylor et al use air flow that is directed obliquely to the front of a protective enclosure.
U.S. Pat. No. 4,100,847--Norton discloses a laminar flow cabinet wherein a transparent vertically movable front closure panel covers all or part of the front and a laminar flow is obtained from a filter mounted in the top and the peripheral edges of a bottom panel, spaced from the sidewalls to define a duct leading to a fan. The air moves upwardly in a duct in the rear wall and downwardly in an air curtain to the gap between the bottom panel and the sidewalls.
Protected enclosures of the foregoing types are useful for certain applications which require the exclusion of airborne particles. However, the devices are arranged for substantially enclosing the protected area and do not permit a great deal of access for manual operations, or other features that are useful with respect to surgical procedures. Air flow installations for surgical procedures on the other hand have been characterized by attempts to avoid structures which confine the area to be protected. In U.S. Pat. No. 4,063,495--Duvlis, filtered air is emitted from an exhaust head directed at a patient's appendage and is collected at a suction head across from the appendage. The device does not exclude particulate matter entering the air stream from the ambient air. U.S. Pat. No. 4,045,192--Eckstein et al discloses a mobile device that simply emits clean air toward the patient. U.S. Pat. Nos. 3,462,920 and 3,511,162, to Denny and Truhan respectively, disclose clean air devices attempting to encompass a patient's bed. As with Duvlis, such devices do not exclude particulate matter entering the air stream from the ambient air.
In connection with surgical equipment, it is known to arrange an entire operating room to define a laminar flow of filtered air from the ceiling to the floor. A room configured in this manner is shown, for example in Turner, Journal of Bone and Joint Surgery, 56-A(2), page 431, 1974. Reference can also be made to U.S. Pat. Nos. 4,060,015 and 3,626,837, both to Pelosi, Jr. Such an installation must be built into the structural members of the operating room.
It is at times desirable to provide a sterile environment within an otherwise relatively pathogen laden area. For example, in the event of minor surgical procedures or for expediency in connection with battlefield surgery or mass casualty disasters and the like, it may not be possible or cost effective to arrange a full scale operating room environment. Nevertheless, the surgeon requires full access to the operative site of the patient, and furthermore, it is generally necessary to provide full access to such area for at least two persons. There is a need to provide the sterility advantages and the full access attributes of full size clean room apparatus, but also to provide a means by which this can be packaged in a small and mobile fixture for use in any environment.
Laboratory animal surgery is a particularly good application of a device as proposed. Small laboratory animals such as mice, rats, rabbits, etc., are often quartered in high density housing arrangements, some having individual cage box ventilation and individual watering hookups, the cage boxes being normally housed in a rack, as shown for example in U.S. Pat. Nos. 4,343,261 and 4,402,280--Thomas. The occupants of the cages may represent various experiments requiring surgical procedures at one time or another. When conducting surgical procedures on a number of subjects, a mobile operating chamber would allow the surgeon to bring the clean environment into convenient proximity with the animal housing system or a researcher's laboratory, and to perform necessary procedures on the occupants of individual cages. However, it should be noted that the environment of the animal housing system may have a high density of airborne particles due to dust and dander associated with the animals. A high performance device allowing substantially complete isolation of the surgical subject (or at least the operative site), essentially bathing the operative site in HEPA filtered laminar air flow, and also permitting complete access to the subject by at least two persons and mobility, would facilitate experimentation or surgical manipulation of the surgical subject in a practical and efficient manner.
The present invention provides a laminar flow isolation apparatus resembling a laboratory hood enclosure, but with full access and visibility from opposite sides of an operating field. A flow of HEPA filtered class 100 air passes vertically downwardly over the subject, this air being substantially less contaminated than the class 10,000 air which characterizes the typical full size operating room. The air is filtered through a block of filter material disposed in a mobile base cabinet and brought to a plenum over the operating field by means of a duct formed by a hollow endwall of the enclosure. The plenum in the top has an array of openings, which can be inclined to increase air flow adjacent the sidewalls to form an air curtain isolating the clean air flow from the outside. The air from the top moves downwardly to corresponding openings in the base of the operating field, namely the upper wall of the cabinet, through which a portion of the air is recycled through the filter. The surgeon(s) and assistants having full access from opposite sides of the mobile enclosure are nevertheless completely removed from the operating area, only the hands and forearms coming into the protected space. This helps to facilitate maximum patient protection by minimizing possible patient operative site contamination from the surgical team's faces, foreheads, necks, and other areas not routinely covered by traditional operating room attire (i.e., caps, masks, gloves and gowns). A positive static pressure is maintained between the enclosure and the outside. . This feature is important for preventing operative site contamination from areas outside the enclosure. Particularly together with means defining an air curtain at the opening, the aspect of excluding outside particles provides the ability to conduct aseptic surgical technique in remote areas such as battlefields and on the site of mass casualty events. Surgical necessities and conveniences are preferably included, for example temperature control apparatus for the filtered air and preferably for the base. Ports in at least one endwall allow access for moving a surgical subject into the enclosure and/or to seal over connection lines traversing the walls of the enclosure. A viewing apparatus in the form of a movably mounted microscope can be directed at the operating field as needed for performing microsurgical procedures and has a viewing port mounted on an extension to protrude from the enclosure through the openings provided for manual access.